A conventional image forming device is provided with a fixing unit that fixes a toner image transferred from a photosensitive unit onto a sheet of paper.
One of such conventional fixing units includes a heat roller, a pressure pad disposed in opposition to the heat roller, and a fixing belt interposed between the heat roller and the pressure pad.
In this fixing unit, the fixing belt can press the heat roller with a large contact area by the pressure applied from the pressure pad, facilitating efficient fixation of toner images. But, at the same time, the pressure pad is required to be in close contact with the heat roller via the fixing belt.
To this effect, laid-open Japanese patent application publication No. 2003-5553 discloses a fixing unit including a heat roller, an endless fixing belt, and a pressure member disposed inside the endless belt. The pressure member is provided with a nip head member for pressing the belt against the surface of the heat roller. The pressure member is attached to an arm member via a belt guide member, and the arm member has one end portion serving as a pivot portion for pivotal movement of the arm member. The nip head member presses the endless belt in a direction toward the vicinity of the center of the heat roller.
In the above-described configuration, since the pressure member is fixed to the arm member, accurate positioning of the pressure member relative to the heat roller at the time of assembly is required so that the nip head member can be in close contact with the heat roller irrespective of the pivotal movement of the arm member. However, demand for such high positioning accuracy necessitates less product tolerance and leads to time-consuming assembly.
In view of the forgoing, it is an object of the present invention to provide a heat fixing unit with a simple structure capable of achieving close contact between a pressure pad and a heat roller, and to provide an image forming device including such a heat fixing unit.